Among lead acid car starter batteries, a lead acid battery to be mounted in cars equipped with idling stop system is supposed to be deeply discharged to a relatively low state-of-charge (SOC) region, and therefore, required to have durability against repeated deep discharge. Patent Literature 1 discloses a technique of optimizing the mass ratio between positive and negative electrode active materials, on the basis of the results of cycle life test conducted after batteries are overdischarged. Patent Literature 2, in order to improve the cycle life characteristics under more practical idling stop conditions, discloses likewise a technique of optimizing the mass ratio between positive and negative electrode active materials. The optimum range of the P/N ratio of mass P of positive electrode active material to mass N of negative electrode active material is from 0.77 to 1.43 in Patent Literature 1, and from 0.91 to 1.43 in Patent Literature 2.